CO2 dilution coefficients for pump sampling method - GMP251 - GMP80P

GMP251 and GMP80P User Guide
Document code
M211799EN
Revision
K
Language
English
Product
GMP251
GMP80P
Document type
User guide

When using drying tubing (for example, Nafion) for sampling, the CO2 concentration of the dry sample will be slightly higher than in the wet sample. This is due to water condensing off the warm, humid gas sample as it cools down. In a sampling environment with humidity and temperature higher than ambient air, the CO2 concentration is diluted by the volume that the water vapor occupies. If water vapor is removed from the sample, the fractions occupied by other gases, including CO2, will increase accordingly.

CO2 dilution coefficients for GMP80P sampling methods at 23 °C (±2 °C) ambient temperature lists the three sampling methods of GMP80P and gives the dilution coefficients for each type of method. When you have the CO2 measurement value shown by Indigo80, you can use the coefficients given in the table to calculate the actual gas concentration in the sampling environment:

  1. On the horizontal axis of the table, select the temperature of the sampling environment (for example, an incubator).
  2. Using the coefficient given for the temperature and the sampling method in use, multiply the CO2 value shown by Indigo80.

    For example:

    • Sampling method: Nafion + plastic tube
    • Temperature of sampling environment: +37 °C
    • CO2 concentration shown by Indigo80: 5.21 %CO2
    • Actual CO2 concentration in sampling environment: 5 %CO2 (5.21 %CO2 × 0.960 = 5 %CO2)
CO2 dilution coefficients for GMP80P sampling methods at 23 °C (±2 °C) ambient temperature
Temperature of sampled gas (°C)
Method +20 +25 +30 +35 +37 +40 +45 +50 +55 +60
Steel pipe 1.000 1.000 0.995 0.988 0.984 0.976 0.962 0.944 0.922 0.897
Plastic tube 1.000 0.998 0.991 0.982 0.977 0.968 0.952 0.932 0.908 0.881
Nafion + plastic tube 0.991 0.984 0.976 0.965 0.960 0.953 0.939 0.923 0.905 0.885